dart:io | Fix a crash when read was called on a closed socket on Windows.

runtime/bin/socket_patch.dart

Index: runtime/bin/socket_patch.dart
diff --git a/runtime/bin/socket_patch.dart b/runtime/bin/socket_patch.dart
index 311487bc074d0f2b47e04a6de51d7d8dbbf78772..3b9aaae6882d2cd05a4c2718b03724b643815fa2 100644
--- a/runtime/bin/socket_patch.dart
+++ b/runtime/bin/socket_patch.dart
@@ -152,6 +152,7 @@ class _NativeSocket extends NativeFieldWrapperClass1 {
     if (len != null && len <= 0) {
       throw new ArgumentError("Illegal length $len");
     }
+    if (isClosed) return null;
     var result = nativeRead(len == null ? -1 : len);
     if (result is OSError) {
       reportError(result, "Read failed");